Mary spends most of the show berating her colleagues for making shameless jokes about the untimely demise of Chuckles, the WJM-TV children’s clown who’s killed in a freak accident (dressed like a peanut, he’s crushed to death by a rogue elephant…)

While Murray, Lou, Ted and Sue Ann can’t help but be utterly amused by the scenario, Mary is completely offended and sees no humor whatsoever in Chuckles’ sad situation.

Yet during the most somber occasion of all – Chuckles’ funeral – Mary absolutely can’t control herself and bursts out into a full-on belly laugh.

As they say, timing is everything.

I’m reminded of an incident in high school when my best buddy Bob and I were interacting with the school librarian (affectionately nicknamed ‘Bird Legs’ by an uncredited but insightful alum).

BL was lecturing us about the challenges of shelving quartos (oversized books), a topic she clearly found both serious and riveting.

And let me just say it took every ounce of strength I had to quell the burning desire to burst into hysterics. My body quivered, ached and yearned to be freed from its forced captivity.

Finally, I reached that point of no return and started laughing convulsively. Rather than dare look at Bob, I simply placed my hand in front of my face – as if that would conceal the shaking shoulders, flushed face and guttural sounds.

I can’t fathom that Bird Legs didn’t know exactly what was happening, yet she just continued her lecture on large books. Which, of course, acted as jet propulsion fuel to our hysteria.

Never was I so grateful to hear the tone that signaled the end of class.

I suspect it may not have been BL’s first encounter with hysterical students. And although she probably didn’t appreciate our poorly timed revelry, the incident did forever create a special place in our hearts for libraries, quartos – and birds.

Neuroscientists have discovered that our brains actually “get ready to laugh” whenever we hear laughter, suggesting that the activity is meant to be shared.

Individual senses of humor vary, but laughter is universal. On average, people do it about 18 times a day. It’s so embedded into our humanity that babies laugh before they speak. Beyond producing endorphins that make us feel better, laughter also can relax muscles, lower stress hormones, boost the immune system and prevent heart disease.

Lots of physical and emotional benefits, to be sure.

If only it could be corralled.

Mary Tyler Moore 20th Anniversary (Chuckles excerpt begins at 1:20):

Learn about the psychology of laughter from UCLA Professor Sophie Scott: